Magnetic control conveying furnace



Dec. 22, 1931. E. 1... SMALLEY v MAGNETIC CONTROL CONVEYING FURNACE Filed Sept. 3. 1929 2 Sheets-Sheet 1 .Z/rze Vbziaye Dec. 22, 1931. SMALLEY 1,837,497

MAGNETIC CONTROL CONVEYING FURNACE Filed Sept. 5, 1929 2 Sheets-Sheet 2 Patented Dec. 1931 UNITED STATES nnwm L. may, or m wrsconsm, ASSIGNOR TO .rmvr mmr 1mm PATENT OFFICE} TRIO OOIIANZOF MILWAUKEE, WISCONSIN, A. CORPORATION OI WISCONSIN mennrrccon'rnor come rumucn Application fledQeptember a, 1929. mm 110. 390,047.

My invention relates broadly to heat-treatment furnaces and more. particularly to furprovide a construction of furnace of the conveyor type wherein material possessing magnetic properties may be moved through the furnace automatically, depending upon the condition of or change in the magnetic properties thereof while being subjected to hea treatment. Another object of my invention is to provide a heat treatment furnace of the endless conveyor type wherein magnetic material may be advanced through the furnace automatically in accordance with the ma etic properties of the material which is en jected to heat treatment whereby the material ma be advanced through the furnace when a c ange in the magnetic condition thereof occurs. 4

A further object of my invention is to provide a construction of heat treatment furnace in which the movement of magnetic material under heat treatment through the furnace is automatically controlled by the magnetic condition of the material under heat treatment, with means for compensating or balancing the control circuits to insure precision in operation.

Other and further objects of my invention will be understood from the specification hereinafter following by reference to the accompanying drawings, in which: 7

Figure 1 illustrates diagrammatically the application of the magnetic control system of my invention to a heat treatment furnace of the conve or type in which the movement of the material through the furnace is determined by the magnetic properties of the material which is subjected to heat treatment;

Fig. 2 illustrates in perspective view the magnetic control system of my invention showing the principle of operation by which the material may be moved through the furnace in accordance with changes in the'magnetic properties of the material; and

Fig. 3 illustrates one form of control circuit which I employ for compensating or adjusting the magnetic-system to insure operation of the control circuit under conditions of change in the magnetic properties of the material under heat treatment.

My invention is directed to an arrangement of magnetic control device for heat treatment furnaces wherein the charge may be automatically moved through the heat treatment furnace under control of the magnetic properties of the charge. That is, when the point is reached at which the steel or other magnetizable material under heat treatment changes its'magnetic properties upon heating, a control circuit is actuated serving to operate driving mechanism by which the charge may be advanced through the furnace. My invention makes use of the principle that steel or other magnetizable metal changes its magnetic properties when heat d to certain temperature, depending upon the analysis of the steel. This change of mag netic properties, occurring at a positive transformation or critical point in the steel, es-

tablishes when known, a reference point in the heat treatment.

My invention provides for magnetically controlling a movable actuator for advancing the conveyor at the time that the steel or other metal under heat treatment changes its magnetic properties,'or reaches a definite transformation point, so that the proper heat treatment may be applied to the charge.

In the system of my invention a heat treatment furnace is provided with any form of heating means, such as gas, or other fuel, or resistors which are electrically energized. In magnetic relationship to the heat treatment chamber .and either dependent or independent of the heating means, I provide a magnetic system which may include a primary coil and a secondary coil inductively related thereto and energized thereby, or a single .winding may be employed. Where primary and secondary windings are provided, the

secondary circuit may include an indicator connected through a compensator circuit for the adjustment of the control system depend ing upon the condition of the load as fully described in the copending application by William B. Cooley, filed September 3,- 1929, Serial Number 390,162, entitled Magnetic control equipment.

In other furnaces I may provide a magnetic circuit magnetically related to the heat treatment chamber in which the air gap, thus included, is changed by the introduction into the air gap of magnetizable material to be heat treated, thereby changing the magnetic conditions. Predetermined magnetizing force may be supplied to the magnetic circuit and the change in magnetic conditions, or the critical transformation points of the material to be heat treated, may be utilized to operate a control device and thereby the character of subsequent heat treatment to be given material within the chamber may be controlled. In conveyor type furnaces, the change in magnetic conditions ma be utilized to control the advancement of the material under heat treatment through the furnace.

In Fig. 1, my invention is shown as applied to a conveyor type furnace where the charges 1 are carried on a moving conveyor 2 which passes through the furnace chamher 3. Any desired form of mechanism for moving the conveyor 2 may be employed and for purposes of illustration, I have indicated in Figs. 1 and 2 an electric motor 4 driving the conveyor 2 which is supported on drums 16 and 17 and driving through gear system 18. A magnetic circuit 5 is provided which surrounds the charges within the furnace as shown. A magnetic winding 30 is provided on pole piece 7 to establish a permanent field through the furnace chamber 3 by energy supplied from line 31. The charges 1 on the conveyor 2 may be aligned with the directly opposite pole members 6 and 7 for concentrating a magnetic field established from winding 30 in a path which passes through the charge 1. So long as the charge 1 possesses a susceptibility to magnetism or up to its critical transformation point, a relatively strong flux passes through the magnetic circuit and the conveyor 2 is stationary due to the fact that the circuit to the motor 4 is opened at contacts 8 by contactor 9 energized by solenoid 10 which connects to winding 11. Winding 10 is energized upon predetermined potential values but is not sufliciently energized when the flux in the magnetic circuit 15 falls below a predetermined value due to change in the mag netic properties in the charge 1. Contactor 9 drops, establishing connection across contacts 8, starting the driving motor 4, and moving the charge 1 out of heat treatment position, and moving the succeeding charge into heat treatment position automatically.

Fig. 2 illustrates more clearly theendless conveyor system by which successive charges 1, 12, 13, 14 and 15 are moved into heat treatment position automatically in accordance with the conditionof the material under heat treatment. It may be noted by reference to this figure that the charge 1, when progressed from the position shown, may be immediately discharged from the conveyor. Or, if the pole pieces are placed at a point further from the discharging end of the conveyor, such portions of the charge could be subjected to any predetermined time of soaking at a given temperature, as is required in some of the alloy steels. In the latter case I may provide a separate automatic control for such soaking temperatures.

Fig. 3 illustrates one form of compensator system used in the circuits of Figs. 1 and 2, which may be employed in balancing the circuits preparatory to a heat treatment operation. The galvanometer 19 is illustrated as including a field winding 20 which is connected with the terminals 21 of the power supply line which supplies the primary circuit 22. The moving coil 23 of the galvanometer connects in series with the secondary circuit including secondary coil 24 and in circuit with a balancing coil or reactance 25, and in series with the motor control switch 9-10. The balancing coil or reactance 25 is tapped at intervals along the length thereof as indicated at 26 and adjustable contact made by means of moving member 27. When the magnetizable charge is introduced into the heat treatment chamber 3, the magnetic flux which passes through the gap within the furnace chamber is augmented and the galvanometer or similar instrument is deflected from its balanced position. When the steel or magnetizable material during the heat treating process changes its magnetic properties to its critical point, the pointer 28 of the galvanometer returns to balanced position. The reactance 25 is adjusted to obtain a predetermined balanced position of the galvanometer. Movement of the galvanometer advises the operator of the magnetic condition of the material which is being subjected to heat treatment within the furnace chamber, as the material is moved through the furnace. By this means a check may be kept during the heat treatment process and the transformation point is readily discernible and permits the concluding of the heating cycle at the proper time. The galvanometer reading enables the circuits to be properly set before commencement of the heat treatment process so that the circuits will be controlled at the transformation point.

While I have shown and described furnaces of the belt type to convey material through the furnace, I may elect to apply the same magnetic circuits and control features in combination with a furnace where the work is progressed through the furnace by means of a pusher, such pusher type furnaces being familiar to those versed in the art.

While I have described my invention in certain of its preferred embodiments, I desire that it be understood that modifications may be made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. In combination, a furnace, a conveyor, work conveyed through said furnace by said conveyor, means for actuating said conveyor, a magnetic circuit whose lines of force pass through said, work and means for automatically controlling said actuating means in response to changes in the intensity of said magnetic circuit.

2. In a furnace of the conveyor t pe, a heat treatment chamber, a conveyor or successively moving charges of magnetizable material to a heat treatment position within said heat treatment chamber, a magnetic circuit disposed adjacent to said heat treatment chamber for subjecting the charges to the path of magnetic flux, means disposed in the path of said magnetic flux and responsive to the changes in the magnitude thereof, driving means for advancing said charges into said heat treatment chamber and means controlled by changes in magnitude of the magnetic flux through each of said charges successively for initiating movement of said driving means.

3. In a heat treatment furnace of the'conveyor type, the method of controlling the heat treatment of magnetizable metal, which consists in moving the magnetizable metal automatically toa position in which said metal is subjected to heat treatment to its final critical temperature passing a magnetic flux through said metal, and automatically moving the metal out of heat treatment position when no magnetic properties exist in said metal.

4. In a heat treatment furnace of the conveyor type a heat treatment chamber, a conveyor for advancing magnetizable material through said heat treatment chamber, driving means for operatinn said conveyor, a magnetic circuit disposed adjacent said heat treatment chamber for establishing a path of magnetic flux through the magnetizable material, means disposed in the path of the magnetic flux and responsive to changes in the magnitude thereof for controlling the operation of said driving means in accordance with the magnetic permeability of each charge which is subjected to heat treatment.

5. In a heat treatment furnace of the conveyor type, the method of automatically controlling the movement of magnetizable metal into heat treatment position within a furnace, subjecting the magnetizable metal to the path of magnetic flux and controlling by the loss of magnetic properties, the successive movement of magnetizable metal into and out of heat treatment position.

6. In combination, a furnace, means for progressing work through said furnace, means for actuating said progressive means, a magnetic circuit whose lines of force pass through said work, and means for automatically controlling said actuatin means when the magnetic properties of sai work disapear. Y a p In testimony whereof I afiix my si ature.

EDWIN L. SMAL EY.

Ill 

